In my example, XXX is the reserved IPP port. So if the admins want to
block outgoing IPP traffic, they tell their routers or firewalls to
not transmit requests to anything on port XXX.
Of course, anyone with an HTTP server on port XXX will be unreachable
from behind such a firewall, and the filter won't block access to IPP
servers on other ports. But that's an inherent limitation of firewalls -
they can't really filter out all unwanted traffic, they can only filter
out most of it.
As long as IPP is run on a separate port, I'm pretty ambivalent
about PRINT vs. POST.
Keith